To understand the role of the kallikrein-kinin system in the kidney, it is necessary to know where kinins are formed. It has been shown that kallikrein arises from the distal tubule. We have found kininogen in the tubule and in urine and believe that kinins are formed in the tubule. Methods are under development to assay, purify, characterize and determine the significance of urokininogen. We want to know if urokininogen is the source of renal kinin.